How to efficiently concatenate strings in go

Question

In Go, a string is a primitive type, which means it is read-only, and every manipulation of it will create a new string.

So if I want to concatenate strings many times without knowing the length of the resulting string, what's the best way to do it?

The naive way would be:

var s string for i := 0; i < 1000; i++ {     s += getShortStringFromSomewhere() } return s 

but that does not seem very efficient.

Answer 1

New Way:

From Go 1.10 there is a strings.Builder type, please take a look at this answer for more detail.

Old Way:

Use the bytes package. It has a Buffer type which implements io.Writer.

package main  import (     "bytes"     "fmt" )  func main() {     var buffer bytes.Buffer      for i := 0; i < 1000; i++ {         buffer.WriteString("a")     }      fmt.Println(buffer.String()) } 

This does it in O(n) time.